The present invention is in the field of oil exploration and drilling. In particular, the present invention is a mobile land rig and method for the rapid placement, assembly, disassembly, and repositioning of an oil drilling rig and associated drilling equipment.
Conventional oil drilling and exploration in major land drilling operations require the rapid deployment, assembly and disassembly of drilling structures. Consequently, the transportability of components and the speed at which components can be assembled with the minimum amount of auxiliary equipment are paramount concerns. A transportable oil drilling rig typically includes, for example, a support base, a mast, pipe sections, and a drill floor. Often times however, auxiliary support equipment such as cranes are required to facilitate the setup and takedown of large components such as the base, the drill floor, the pipe racking board, and the like having the effect of increasing operational costs.
Drilling sites are often located in remote areas requiring truck transportation of the components of the rig accompanied by equipment used to assemble the rig. Further complicating the rig assembly process is the persistent need to change locations once a hole is sunk and it is determined whether the site will be sufficiently productive to merit a pumping installation, whether the site will be unproductive all together, or whether a more ideal location exists to sink a hole. Typically, site changes can occur once every several months, and, in response, prior art systems have attempted to increase the degree of mobility of rig components. Auxiliary equipment however is still necessary for performing steps such as placing the drill floor.
Since the variable costs associated with leased support equipment, such as cranes and the like, are calculated on a per hour or per day basis, expediting the takedown, transport, and setup operations is crucial for minimizing equipment leasing costs. Typical takedown and setup time is in the order of days. With equipment leasing costs ranging from several hundred dollars per day or more, many thousands of dollars in costs may be incurred for each end of a setup and takedown operation. For larger or more complex rigs, the cost may be even higher. In general, prior art drilling rigs are geared towards facilitating rapid setup, takedown and transport but still require external cranes, external winches, and the like which are most often leased increasing overall expense.
One such prior art system for erecting an oil well derrick is shown in U.S. Pat. No. 3,922,825 issued to Eddy""s et al on Dec. 2, 1975. Eddy""s system employs a stationary substructure base and a movable substructure base mounted thereon. Eddy""s movable substructure base is coupled to the stationary base but swings upright into an elevated position on a series of struts that are connected to the stationary base with swivel connections at each end. Eddy""s movable base is otherwise stationary given that neither the stationary base nor the xe2x80x9cmovablexe2x80x9d base are mobile or repositionable without the use of an auxiliary crane or the like. Moreover, simply raising the movable substructure base and the drill mast requires the use of a winch mounted on an auxiliary winch truck.
Another prior art system for assembly of a drill rig is shown in U.S. Pat. No. 3,942,593 issued to Reeve, Jr., et al on Mar. 9, 1976. The mobile well drilling rig apparatus shown in Reeve comprises a trailerable telescoping mast and a separate sectionable substructure assembly further comprising a rig base, a working floor, and a rail means. The mast is conveyed to the top of the substructure by rollers and may be raised by hydraulic raising means to the upright position. Some of the disadvantages of such a system are the sheer length of the mast assembly when transporting and the instability of the mast while raising. A further disadvantage of the system of Reeve is the need for drawlines and winch means to raise the mast onto the working floor.
In addition to the need for auxiliary equipment such as winch trucks and the like, each of the above mentioned systems requires some stationary substructure that must be set down prior to the imposition of any additional structure thereupon. Further movement or repositioning of the base structure requires cranes or other heavy equipment to effect movement even in the case of the purported xe2x80x9cmovablexe2x80x9d base structure of Eddy.
It would be desirable therefore for a mobile land rig that was self sufficient thus capable of being transported, erected, and disassembled without the need for auxiliary equipment. Such a system would save costs associated with leasing cranes and the like for periods of days during erection and disassembly of rigs.
It would further be desirable for a system with a self contained substructure base capable of being easily moved. Such a system would allow rapid placement and repositioning of the substructure base without the need for a crane or the like.
It would still further be desirable for a system having a substructure base that could be telescoped to a maximum operating height and automatically secured at such height yet possess structural rigidity sufficient to withstand winds and like forces incumbent on the mast structure. Further, the desirable system would be able to be collapsed to a minimum height to facilitate transport. Such a system would allow the substructure base to be easily transportable when collapsed yet sufficiently tall to support a drill mast when telescoped.
It would still further be desirable for a system capable of winching components into place with a self contained winching platform located on the drill mast. Such a system would allow rig components to be placed without the need for auxiliary equipment such as an external crane or winch.
It would be still further desirable for a system wherein all system components could be easily trailerable and transportable by truck. Such a system could be easily moved from one site to another with a minimum of setup and takedown time.
To meet the objects of the invention, a mobile land rig is provided for the transport assembly and disassembly of oil drilling equipment. The mobile land rig of the present invention comprises a mobile telescoping substructure box having wheel means integrated therein capable of supporting the mobile telescoping substructure box in rolling relation to the ground or drilling platform surface during transport. The mobile telescoping substructure box in the lowered position facilitates assembly of the mobile telescoping substructure box and the drill mast prior to and during mast erection. The mobile telescoping substructure box is typically raised into the fully extended position once the drill mast is fully erected as described hereinafter.
In the present invention, two such mobile telescoping substructure boxes are used to establish the base for the drill mast. The wheel means for allowing the mobile telescoping substructure box to roll may consist of one or more axle wheel assemblies preferably equipped with conventional heavy duty pneumatic rubber truck tires. The wheel means may further be provided with a selective raising and lowering means, such as a hydraulic lift, within the mobile telescoping substructure box to selectively engage and disengage the wheel assembly with a ground surface by lifting and lowering the substructure box in relation to the wheel means. When the mobile telescoping substructure box is correctly rolled into position, for example, the wheel assembly can be raised relative to the mobile telescoping substructure box and thereby establish direct contact between the ground and support footings or a support frame of the mobile telescoping substructure box. The support frame, in addition to bearing the load of the mobile telescoping substructure box and all structure attached thereto, may be equipped with load leveling means to ensure that the mobile telescoping substructure box is placed on the level.
The mobile telescoping substructure boxes comprise an inner and an outer frame section with the inner frame section nested inside the outer and coupled to the outer frame section by cables. The frame sections may be made from suitable structural, metal, such as steel, with sufficient strength to support the drillworks, racking board, drill floor, drill mast, and the like. To facilitate telescopic extension of the mobile telescoping substructure box while maintaining structural integrity thereof, the inner frame may be rigged with cables made from steel or suitably strong material.capable of withstanding loads generated during rig construction and erection, loads generated from lateral forces such as wind, or loads generated from objects suspended from the drill mast. Such cables may be coupled to the inner frame and the outer frame such that when the frame reaches maximum extension, the cables are drawn taught in a predetermined pattern that enhances the structural characteristic of the mobile telescoping substructure box. Such a pattern may, for example, be a simple crisscross pattern such that lateral forces impinging on one side of the structure are translated through the cable configuration to the opposite side of the structure. In addition to providing support, the cables may be provided with limit switches to signal that the inner frame has reached maximum excursion. Further, turnbuckles may be provided to adjust the cables for the proper tension.
Stop pins are provided on the outer frame section of the mobile telescoping substructure box to secure the inner frame section in the fully extended position. When the mobile telescoping substructure box reaches maximum extension, the stop pins are engaged with stop pin activating means, preferably being hydraulically activated, through the supporting structure of the extended inner frame section to lock the extended inner frame section in place. Stop pins are engaged in response to tension limiters coupled to the cables and capable of sensing when the tension on the cables reaches a predetermined tension value. Such a predetermined tension value is indicative of the full extension of the extended inner frame section. Tension limiters coupled to the cables then signal the hydraulically activated stop pin activating means. The stop pins and activation means may be attached to the outer frame section and may be extended through openings in the outer frame section when engaged. The stop pins support the inner frame in the fully extended position thus facilitating load bearing and preventing retraction of the inner frame into the outer frame section.
To facilitate telescoping and provide guidance and structural support during telescoping, the inner frame may further be located within an enclosed frame rail, guide rail, or like structure. Rollers located either on the inner or outer frame may be used to facilitate smooth telescoping action and reduce friction between the inner and outer frames of the mobile telescoping substructure box. In the preferred embodiment, the mobile telescoping substructure box is telescoped after assembly and erection of the drill mast.
The drill mast forms another part of the claimed invention, typically comprising, in one embodiment, a bottom mast section and a top mast section both being transportable to the drilling site on separate trailers. The bottom mast section may be placed in proximity to the mobile telescoping substructure box trailers. Drawworks for the rig may be located on a separate trailer and placed on the side of the drill cellar opposite the mast trailer. Hydraulic cylinders are provided on the trailer for raising the bottom mast section into position and pinning the bottom mast section to the two respective mobile telescoping substructure boxes. The bottom mast section may be unlinked from the trailer by unpinning the mast from the trailer. The bottom mast section may then be linked to the mobile telescoping substructure box and raised into an erect position by a telescoping hydraulic mast raising cylinder. The bottom mast section is further provided with an A-leg that can lower the profile during transport yet be opened upon erection to provide key support for the erected mast.
The top mast section may be coupled to a separate trailer means. During mast assembly, the top mast trailer means may be backed into position in proximity to the bottom mast section and a protruding end section thereof. The top mast section is joined with the bottom mast section to form the complete drill mast. The bottom mast section is equipped with guides at the protruding end section for facilitating alignment of the top and bottom mast sections. The guides are placed on the bottom mast section in the preferred embodiment since the position of the bottom mast section is adjustable and thus can be moved into alignment using the guides to facilitate attachment of the top and bottom mast sections. The hydraulic mast raising cylinder, in addition to raising the mast, allows the bottom mast section to be adjusted in the vertical direction to facilitate aligning and coupling the top and bottom mast sections. Horizontal adjustment of the position of the bottom mast section may be accomplished with a hydraulically, mechanically, or electrically adjusted means such as a turn screw or a drive motor. Since hydraulic power is readily available on the mobile land rig of the present invention, it is the preferred operative means for working devices on and around the rig.
The drill mast may further be provided with a racking board for racking pipe sections, an operation known in the art. The racking board is folded during transport against the top mast section. To provide an advantageous alternative to an external crane, the racking board may further be provided with a winch on the underside thereof traveling via wheel movement along a rail secured to the racking board and provided with a rack gear thereunder. The winch frame is provided with a pinion gear drive powered by a hydraulic driven motor which engages the rack gear and moves the winch back and forth along the track. A cable reeved around a winch on the drawworks trailer runs up through a roller means and down through the winch trolley for raising and lowering loads. The trolley may be positioned inwardly and outwardly along a rail limited by the length of the racking board and any extension added thereto. In the preferred embodiment, the rail would be coextensive with the length of the racking board, but could be extended beyond the racking board length as limited only by the ability of the structure to support the maximum load calculated as a product of load weight and the rail length. Such a winch and trolley may be used, for example, to lift the drill floor into position. The top mast section aft trailer is also provided with hydraulic lift means to raise the top mast portion to a position where it is ready for erection once the top mast section is pinned to the bottom mast section and the top mast section is released from the top mast section forward trailer. The racking board may be extended outwardly from its retracted position along side the top mast section in preparation for mast erection when the top mast section is raised significantly to clear the ground using the lift means on the aft trailer.